The present invention relates to wire mesh cathodes for electron tubes. In high power, high frequency electron tubes, the cathode occasionally takes on the configuration of a wire mesh or screen. The mesh may consist of an array of wires extending across and welded to another array of wires. Heretofore both arrays contained an equal number of wires. In a closely spaced tube, one of the arrays in the cathode is appreciably closer to the control grid than the other array of wires. The more remote array may be 50% farther from the control grid than the closer array in some tubes. In this case, due to the difference in distance of the arrays from the control grid, 90% of the emission current in the electron tube is emitted from the array closest to the grid.
One of the major design considerations in high powered tubes is heat dissipation. It is therefore advantageous to design a tube which consumes as little filament heater power as possible. In the example noted above, although the remote array carries only 10% of the emission current, in a hot cathode, it absorbs 50% of the filament heater power, thereby consuming an unjustifiable amount of heater power.